Fractal axicons

Cantor rings are rotational symmetric pupils that are generated from a Cantor set of a given level of growth. These pupils have certain fractal properties. For example, it is known that when illuminated by a general spherical wavefront they provide self-similar patterns at transverse planes in the Fraunhofer region. In this paper, we study the response of Cantor rings when illuminated by a Bessel light beam conforming what we call fractal axicons. It is shown that, with this kind of illumination a close replica of the radial profile of the pupil is obtained along the optical axis, i.e., we show that the axial behaviour of these pupils has self-similarity properties that can be correlated to those of the diffracting aperture. The influence of several construction parameters is numerically investigated.     

可见-近红外波段太阳光谱辐照度仪的辐射定标方法研究

为了满足可见-近红外波段太阳光谱的高精度观测需求,对使用细分光谱技术进行太阳直射辐射观测的新型太阳光谱辐照度仪,开展了辐射定标方法的研究。使用光谱辐照度标准灯在400 nm～1 050 nm光谱范围内对仪器进行相对定标,对满足比尔-朗伯定理的波段采用Langley法进行绝对定标,在整个光谱范围内将辐射基准溯源到大气层顶的太阳光谱辐照度。在甘肃敦煌和安徽合肥两地进行了室外比对实验,仪器观测结果和MODTRAN40模型的理论模拟结果一致,和CE318的4个气溶胶观测通道的结果偏差在5%以内,验证了该定标方法的合理性。     

光谱辐射照度量值复现中计算大口径固定点黑体拐点温度的新方法

我国光谱辐射照度基准量值复现的理论基础是普朗克定律,它揭示了波长、温度和光谱辐射照度之间存在着精确的定量关系。采用比较法、通过卤钨灯来进行光谱辐射照度量值的保存与传递。其中,黑体的温度测量在量值复现中是最主要的不确定来源。以往都是采用变温黑体作为量值复现的辐射源,其温度通过高温计溯源至温标固定点黑体。为满足我国对地观测、气象遥感、应对气候变化、海洋水色等领域对光谱辐射照度高精度的测量需求,中国计量科学研究院NIM建立了一套14 mm大口径钨碳-碳WC-C高温固定点黑体系统,作为基准辐射源直接复现光谱辐射照度量值,进一步缩短了量值溯源链,减少了温度测量误差。实验中高温计用来测量黑体的相对温度,采用固定点熔化温坪曲线的拐点POI值校准后得到温度绝对值。因此拐点POI的合理评估计算就十分重要。与小口径WC-C固定点黑体不同,大口径固定点的熔化温坪曲线的持续时间更长,但温度起伏也更大,因此广泛用于小口径固定点的传统拐点POI算法不再适用。提出了一种可筛选多次拟合法,用于计算大口径固定点黑体的拐点温度。采用3 mm小口径WC-C和Re-C固定点对新方法的有效性进行验证,结果表明新方法与三种传统方法的平均值的最大偏差为-0.007和-0.001 K,在500 nm引入的光谱辐射照度测量误差分别为0.002 2%和0.000 3%。进一步采用14 mm大口径WC-C大口径固定点对新方法的稳健性进行验证。分析比较了筛选条件、数据平滑处理、拟合范围对拐点POI计算结果的影响,新方法和三种传统POI计算方法的最大影响量分别为0.001和0.633 K,在500 nm引入的光谱辐射照度不确定度分别为0.000 3%和0.20%。所提出的新方法能够有效减小外界因素引入的温度误差,进一步提升光谱辐射照度量值的复现准确度,更适用于大口径高温固定点黑体拐点温度的计算。     

自动寻日的太阳辐照绝对辐射计

为了准确测量太阳总量辐射,研制了具备自动跟踪能力的太阳辐照绝对辐射计SIAR-3a.介绍了SIAR-3a的原理,提出了双轴太阳跟踪的控制方法.SIAR-3a采用电来标定待测量的太阳总量辐射,可以在测量太阳总量辐射的同时较为准确地跟踪太阳.标定实验中,SIAR-3a在3σ范围内的相对均方根误差是0.06%,已经标定到了保...     

Comment on "Strong signature of the active Sun in 100 years of terrestrial insolation data" by W. Weber

An analysis of ground-based observations of solar irradiance was recently published in this journal, reporting an apparent increase of solar irradiance on the ground of the order of 1% between solar minima and maxima [1]. Since the corresponding variations in total solar irradiance on top of the atmosphere are accurately determined from satellite observations to be of the order of 0.1% only [2], the one order of magnitude stronger effect in the terrestrial insolation data was interpreted as evidence for cosmic-ray induced aerosol formation in the atmosphere. In my opinion, however, this result does not reflect reality. Using the energy budget of Earth's surface, I show that changes of ground-based insolation with the solar cycle of the order of 1% between solar minima and maxima would result in large surface air temperature variations which are inconsistent with the instrumental record. It would appear that the strong variations of terrestrial irradiance found by [1] are due to the uncorrected effects of volcanic or local aerosols and seasonal variations. Taking these effects into account, I find a variation of terrestrial insolation with solar activity which is of the same order as the one measured from space, bringing the surface energy budget into agreement with the solar signal detected in temperature data.     

统计光学与光强、激光散斑、反衬度

本文以统计光学的基本思想和方法讨论光学成象中光强分布，说明散斑的非常随机性和散斑图象中的颗粒状表现，推导反衬度与粗糙程度的关系。     

Effects of irradiation conditions on the weathering of engineering thermoplastics

The nature of the light source and its intensity can be important variables in accelerated weathering of aromatic engineering thermoplastics. Activation spectra show that BPA polycarbonate (PC) and its blends are very sensitive to UV with wavelengths <300 nm, as is well-known in the literature, but other resins gave unremarkable results. Xenon arc weathering experiments performed under identical conditions, but with different filter combinations did not show consistent rate enhancements. For 48 samples across a range of aromatic engineering thermoplastics, conditions using borosilicate inner and outer filters were 1.7× harsher than the CIRA/soda lime filter combination. However, the range was 1.0-2.5 and the standard deviation was approximately 0.35 making the correlation 1.7 ± 0.7 at 95% confidence level for any given sample. The quartz/borosilicate combination used in SAE J1960 was 2.3× harsher than CIRA/soda lime conditions, but the standard deviation was 1.1 making the correlation 2.3 ± 2.2 at the 95% confidence level for any given sample. The effects of irradiance level and the dark cycle were determined in order to establish the legitimacy of accelerated testing methods. Linear increases in degradation with increased irradiance were observed for PC, poly(butylene terephthalate), and blends of PC with other polymers. Some non-linearity was found for styrene acrylonitrile copolymer (SAN), and extreme non-linearity was found for ABS. No effect was found from a light/dark cycle other than the rate reductions expected from the lower dose rate. Thus, for accelerated weathering of engineering thermoplastics, the best possible match for sunlight is required, but increasing the intensity and decreasing or eliminating the dark period are permissible for most aromatic thermoplastic resins.     

自动寻日的太阳辐照绝对辐射计(英文)

为了准确测量太阳总量辐射,研制了具备自动跟踪能力的太阳辐照绝对辐射计SIAR-3a。介绍了SIAR-3a的原理,提出了双轴太阳跟踪的控制方法。SIAR-3a采用电来标定待测量的太阳总量辐射,可以在测量太阳总量辐射的同时较为准确地跟踪太阳。标定实验中,SIAR-3a在3σ范围内的相对均方根误差是0.06%,已经标定到了保存在瑞士达沃斯世界辐射中心的世界辐射基准。太阳辐照实验结果表明,SIAR-3a工作可靠,测量结果准确。     

菲涅耳聚光系统下砷化镓电池输出特性研究

对理论聚光比为676的菲涅耳聚光系统下单片砷化镓太阳电池及由六片砷化镓电池的串联组件的输出特性进行分析。建立三结砷化镓电池输出特性的单指数数学模型,并与实验进行了对比。理论计算与实验吻合较好,误差在7.6%以内。实验结果表明,在相同理论聚光比下,单片电池系统能流聚光比为390,六片电池组件系统能流聚光比为281;聚光后单片电池的短路电流与峰值功率分别放大322倍与316倍,六片电池组件系统的短路电流与峰值功率分别放大275倍与272倍;电池表面能流密度为0.321MW/m2时电池的输出功率达到最大,电池表面温度高于323K将影响其工作稳定性;聚光系统的透射率每增加0.01系统效率升高约0.227%。全天累积直射辐照度为17.212MJ/m2条件下测得单片电池全天发电量为0.015kW.h,六片电池串联组件的全天发电量为0.076kW.h。     

高温黑体性能评定和温度测量

中国计量科学研究院引进了高温黑体BB3500M作为新的光谱辐射照度基准光源。黑体BB3500M包括辐射腔体和温度反馈系统。辐射腔体由一系列高温热解石墨环组成,可以加热至3 500 K。在光谱辐照度测量中,高温黑体的性能参数和温度测量至关重要。对于黑体的性能参数,着重考察了黑体温度的稳定性和腔底温度的均匀性。在将高温黑体的光谱辐射照度传递给工作标准灯时,黑体的温度可能发生改变。实验观测了一小时内黑体的温度漂移情况。当高温黑体加热至3 016 K时,采用温度反馈系统的BB3500M稳定在0.3 K。实验光路中设置了限制光栏,用于屏蔽来自黑体腔壁的辐射。黑体腔底辐射环的温度均匀性优于0.2 K。在温度测量中,2 473 K以下的温度可以直接溯源到中国计量科学研究院热工处,对于更高温度的测量需要进行温度延伸。文中从普朗克公式出发,通过多波长亮度比较法进行了温度延伸。实验先在低温区进行延伸证实了方法的可能性,然后进行了高温区的温度延伸。